feat: add task creation, deletion, and modal focus restoration

Implemented task creation flow with keyboard shortcut (c) and UI button. Added task deletion with confirmation dialog,
accessible via Delete key or per-row delete button. Fixed modal close behavior to restore
focus and reselect the appropriate task (created task for new tasks, original task for view/edit).
Enhanced tag and project autocomplete with hierarchical project suggestions and tag filtering

docs/keyboard-shortcuts.md

@@ -69,6 +69,9 @@ These shortcuts work when the task table has focus:
 | Shortcut | Action |
 |----------|--------|
 | `Enter` | Open selected task details |
+| `e` | Edit selected task |
+| `c` | Create new task |
+| `Delete` | Delete selected task (with confirmation) |
 | `←` | Collapse current project |
 | `→` | Expand current project |
 
@@ -203,16 +206,56 @@ These shortcuts work when a filter dropdown (Status/Priority/Due) has focus:
 | `Ctrl+H` | Focus previous filter element |
 | `Ctrl+J` | Focus table headers |
 
-## Modal (Task Details)
+## Modal (Task Details - View Mode)
 
 These shortcuts work when viewing task details:
 
 | Shortcut | Action |
 |----------|--------|
-| `Escape` | Cancel edit (when editing) or close modal |
+| `Escape` | Close modal |
+| `e` | Enter edit mode |
 | `j` / `↓` | Scroll down |
 | `k` / `↑` | Scroll up |
-| `Ctrl+Enter` | Save edits (when editing) or close modal |
+
+## Modal (Task Details - Edit Mode - Navigating)
+
+These shortcuts work when editing a task but not actively typing in a field:
+
+| Shortcut | Action |
+|----------|--------|
+| `Escape` | Close modal (prompts if unsaved changes) |
+| `Ctrl+S` | Save changes |
+| `j` / `↓` / `Tab` | Focus next field |
+| `k` / `↑` / `Shift+Tab` | Focus previous field |
+| `Enter` / `Space` | Edit focused field or item |
+| `Delete` / `Backspace` | Delete selected item (tag/annotation) |
+| `h` / `l` | Navigate between items (tags/annotations) |
+| `u` | Undo last change |
+| `r` | Redo last undone change |
+| `y` | Confirm action (in delete dialogs) |
+| `n` | Cancel action (in delete dialogs) |
+
+## Modal (Task Details - Edit Mode - Typing)
+
+These shortcuts work when actively typing in an input field:
+
+| Shortcut | Action |
+|----------|--------|
+| `Escape` | Exit field (return to navigation) |
+| `Ctrl+S` | Save all changes |
+| `Enter` | Submit field or exit (depends on field type) |
+
+## Modal (Task Details - Edit Mode - Dropdown Open)
+
+These shortcuts work when a dropdown (Priority/Status) is open:
+
+| Shortcut | Action |
+|----------|--------|
+| `Escape` | Close dropdown |
+| `Ctrl+S` | Save all changes |
+| `Enter` / `Space` | Select option and close dropdown |
+| `j` / `↓` | Select next option |
+| `k` / `↑` | Select previous option |
 
 ## Search Input Editing